U.S. patent number 8,690,118 [Application Number 12/684,379] was granted by the patent office on 2014-04-08 for solenoid actuated device and methods.
This patent grant is currently assigned to Caterpillar Inc.. The grantee listed for this patent is Nadeem N. Bunni, Stephen R. Lewis, Jayaraman K. Venkataraghavan. Invention is credited to Nadeem N. Bunni, Stephen R. Lewis, Jayaraman K. Venkataraghavan.
United States Patent |
8,690,118 |
Bunni , et al. |
April 8, 2014 |
Solenoid actuated device and methods
Abstract
A solenoid actuated device such as a fuel injector includes an
actuator body having a plurality of body pieces, and a single-pole
solenoid actuator assembly positioned at least partially within the
actuator body. The single-pole solenoid actuator assembly includes
a one-piece compound armature housing having a load carrying
component clamped between the first body piece and the second body
piece, and a flux carrying component. The load carrying component
includes a high structural strength and a low flux permeability,
and the flux carrying component includes a low structural strength
and a high flux permeability. A method of making a solenoid
actuated device includes placing an armature at a sliding radial
air gap with a flux carrying component of a one-piece compound
armature housing, and establishing a structural load path by
placing a load carrying component of the compound armature housing
between a first actuator body piece and a second actuator body
piece. A method of operating a single-pole solenoid actuator device
includes supporting a flux carrying component of a one-piece
compound armature housing with a load carrying component of the
compound armature housing, channeling magnetic flux across a
sliding air gap between a flux carrying component and the armature,
and channeling a clamping load between a first actuator body piece
and a second actuator body piece through the load carrying
component of the compound armature housing.
Inventors: |
Bunni; Nadeem N. (Cranberry,
PA), Venkataraghavan; Jayaraman K. (Dunlap, IL), Lewis;
Stephen R. (Chillicothe, IL) |
Applicant: |
Name |
City |
State |
Country |
Type |
Bunni; Nadeem N.
Venkataraghavan; Jayaraman K.
Lewis; Stephen R. |
Cranberry
Dunlap
Chillicothe |
PA
IL
IL |
US
US
US |
|
|
Assignee: |
Caterpillar Inc. (Peoria,
IL)
|
Family
ID: |
44257778 |
Appl.
No.: |
12/684,379 |
Filed: |
January 8, 2010 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20110168813 A1 |
Jul 14, 2011 |
|
Current U.S.
Class: |
251/129.16;
239/585.3; 239/585.5 |
Current CPC
Class: |
F02M
47/027 (20130101); F02M 63/0021 (20130101); H01F
7/1638 (20130101); Y10T 29/4902 (20150115) |
Current International
Class: |
F16K
31/02 (20060101) |
Field of
Search: |
;251/129.15,129.16
;239/585.1-585.5 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Self-Guided Armature in Single Pole Solenoid Actuator Assembly and
Fuel Injector Using Same; U.S. Appl. No. 12/321,809, filed Jan. 26,
2009. cited by applicant.
|
Primary Examiner: Fristoe, Jr.; John K
Assistant Examiner: Paquette; Ian
Attorney, Agent or Firm: Liell & McNeil
Claims
What is claimed is:
1. A solenoid actuated device comprising: an actuator body
including a first body piece having a first clamping surface, a
second body piece having a second clamping surface, and a clamping
mechanism which includes a release state and a clamping state; a
single-pole solenoid actuator assembly positioned at least
partially within the actuator body and including a stator, an
armature movable relative to the stator, and a movable pin coupled
with the armature; the single-pole solenoid actuator assembly
further including a one-piece compound armature housing defining a
longitudinal axis and including an outer radial surface and an
inner radial surface defining a guide bore for the movable pin, the
compound armature housing having a load carrying component clamped
between the first clamping surface and the second clamping surface,
and a flux carrying component supported by the load carrying
component and defining a sliding air gap with the armature, the
load carrying component having a high structural strength and a low
flux permeability, and the flux carrying component having a low
structural strength and a high flux permeability, wherein the
compound armature housing has a stepped configuration defining a
first axial segment which includes the flux carrying component and
the load carrying component, and a second axial segment which
includes the guide bore; and a spacer positioned axially between
the first axial segment of the compound armature housing and the
second body piece, wherein the first clamping surface contacts the
first axial segment of the compound armature housing and the second
clamping surface contacts the spacer.
2. The solenoid actuated device of claim 1 wherein the first axial
segment defines a first radial air gap between the outer radial
surface and the second body piece and the second axial segment
defines a second radial air gap between the outer radial surface
and the second body piece which is smaller than the first radial
air gap.
3. The solenoid actuated device of claim 2 wherein the movable pin
includes a valve control pin movable between a first pin position
and a second pin position, and the solenoid actuated device further
includes a control valve mechanism positioned at least partially
within the second body piece and being controllably coupled with
the valve control pin.
4. The solenoid actuated device of claim 1 comprising a fuel
injector, wherein the first body piece includes a stator housing,
wherein the second body piece includes a fuel injector valve body
defining a fuel inlet, and wherein the actuator body further
includes a fuel injector nozzle body defining at least one nozzle
outlet in fluid communication with the fuel inlet.
5. The solenoid actuated device of claim 4 wherein: the stator
housing includes a first stator housing end which includes the
first clamping surface, and a second stator housing end; the
actuator body further includes a fuel injector cap having a third
clamping surface contacting the second stator housing end, the
stator housing being clamped between the fuel injector cap and the
compound armature housing; and the clamping mechanism includes a
first set of threads located on the fuel injector cap and a second
set of threads located on the second body piece.
6. The solenoid actuated device of claim 5 wherein the stator
includes a first axial end surface defining an axial air gap with
the armature, and wherein the load carrying component includes a
second axial end surface contacting each of the first axial end
surface and the first clamping surface.
7. The solenoid actuated device of claim 5 wherein: the flux
carrying component includes a flux ring having a flux ring inner
radial surface adjoining the sliding air gap, a flux ring outer
radial surface, and a flux ring radial thickness between the flux
ring inner radial surface and the flux ring outer radial surface;
and the load carrying component includes a flux ring support cup
having a support cup inner radial surface contacting the flux ring
outer radial surface, a support cup outer radial surface and a
support cup radial thickness between the support cup inner radial
surface and the support cup outer radial surface which is less than
the flux ring radial thickness.
8. A method of making a solenoid actuated device comprising the
steps of: establishing a magnetic flux path for a single-pole
solenoid actuator at least in part via the steps of placing an
armature at an axial air gap with a stator, and placing the
armature at a sliding radial air gap with a flux carrying component
of a one-piece compound armature housing; establishing a structural
load path for the single-pole solenoid actuator at least in part
via a step of placing a load carrying component of the one-piece
compound armature housing between a first actuator body piece and a
second actuator body piece; clamping the one-piece compound
armature housing between the first actuator body piece and the
second actuator body piece; and magnetically isolating the compound
armature housing from the second actuator body piece at least in
part via the steps of placing the compound armature housing at a
radial air gap with the second actuator body piece, placing a first
axial segment of the compound armature housing at a first radial
air gap with the second actuator body piece, the first axial
segment including the flux carrying component and the load carrying
component, and placing a second axial segment of the compound
armature housing at a second radial air gap with the second
actuator body piece which is smaller than the first radial air gap,
the second axial segment defining a guide bore for a movable member
coupled with the armature.
9. The method of claim 8 further comprising a step of placing a
spacer axially between the first axial segment and the second
actuator body piece, wherein the step of establishing a structural
load path further includes establishing a structural load path that
includes the spacer.
10. The method of claim 8 further comprising the steps of forming
the flux carrying component in an annular shape, and securing the
flux carrying component within an axial segment of the compound
armature housing which includes the load carrying component.
11. A method of operating a single-pole solenoid actuated device
comprising the steps of: supporting a stator, an armature and a
one-piece compound armature housing, of a single-pole solenoid
actuated device, within an actuator body, the actuator body
including a first body piece having a first clamping surface, a
second body piece having a second clamping surface, and a clamping
mechanism, the compound armature housing including a stepped
configuration defining a first axial segment which includes a load
carrying component; supporting a flux carrying component within the
one-piece compound armature housing with the load carrying
component of the one-piece compound armature housing via a step of
positioning a spacer axially between the first axial segment of the
compound armature housing and the second body piece; channeling
magnetic flux across a sliding air gap between the flux carrying
component and the armature; and channeling a clamping load between
the first actuator body piece and the second actuator body piece
through the load carrying component of the one-piece compound
armature housing via a step of clamping the load carrying component
between the first clamping surface and the second clamping surface,
wherein the first clamping surface contacts the first axial segment
of the compound armature housing and the second clamping surface
contacts the spacer.
12. The method of claim 11 wherein the first actuator body piece
includes a stator housing, and wherein the step of channeling a
clamping load further includes channeling a clamping load which
includes a first load path segment through the stator housing, a
second load path segment through the load carrying component and a
third load path segment through a spacer positioned between the
load carrying component and the second body component.
13. The method of claim 12 further comprising the steps of:
energizing a solenoid of the single-pole solenoid actuated device;
and moving a valve control pin coupled with the armature from a
first pin position to a second pin position in response to
energizing the solenoid; and moving a valve member coupled with the
valve control pin from a first valve position to a second valve
position by way of a fluid pressure, during the step of moving the
control pin.
14. The method of claim 13 wherein the single-pole solenoid
actuated device includes a fuel injector, and wherein the step of
moving a valve member further includes moving a check control valve
member of the fuel injector, the method further comprising a step
of moving an outlet check of the fuel injector from a closed
position to an open position in response to moving the check
control valve member.
Description
TECHNICAL FIELD
The present disclosure relates generally to solenoid actuators, and
relates more particularly to channeling a magnetic flux and a
structural load through a compound armature housing in a
single-pole solenoid actuator assembly.
BACKGROUND
A wide variety of solenoid actuators and solenoid actuated devices
are known in the electromechanical arts. Solenoid actuators may be
broadly classified as having dual-pole or single-pole solenoids. In
most dual-pole solenoid designs, an armature is spaced at an axial
air gap with a stator having a coil embedded therein. Dual-pole
solenoids are often identified by an armature diameter that is
about the same or greater than an outer diameter of the coil
winding of the stator. When the coil in a dual-pole solenoid is
energized, magnetic flux is generated around the coil, and flux
lines pass through the stator, to the armature and back to the
stator. The resulting flux path produces a pair of magnetic north
and magnetic south poles between the stator and armature on each
side of the axial air gap. The flux between these poles is
generally parallel to the armature motion. These opposite poles
produce a force on the armature that tends to move it toward the
stator and coil to accomplish some task, such as opening or closing
a valve.
In a typical single-pole solenoid, the magnetic flux path also
encircles the coil and passes through the stator, the armature and
back to the stator. The resulting flux path also produces a pair of
magnetic north and south poles between the stator and the armature.
In contrast to dual-pole configurations, the flux path between the
poles is parallel to armature motion for one set of poles, and
perpendicular to armature motion for the other set of poles. The
perpendicular portion of the flux path may traverse a sliding
radial air gap between the armature and another electromagnetic
component that is present to complete the magnetic circuitry.
Single-pole solenoids are often identified by an armature diameter
that is smaller than the inner diameter of the coil winding of the
stator. Due at least in part to manufacturing considerations, the
additional electromagnetic component that is present in single-pole
solenoids is often not a part of the stator itself. Rather, it is
generally in contact with or positioned very close to the stator.
The extra electromagnetic component is also typically stationary,
hence the description of the air gap between this extra component
and the armature as a "sliding radial air gap." Single-pole
solenoids remain preferred in certain applications.
The extra electromagnetic component mentioned above is often
referred to as a magnetic flux ring. It is common to use materials
such as iron and silicon iron to form the flux ring component.
While such flux rings have worked well in certain designs, they are
often associated with leakage of magnetic flux out of the desired
flux path. In addition, because such flux rings are typically made
of materials that are not only magnetically conductive, but also
electrically conductive, eddy currents can form within the flux
ring. The eddy currents create magnetic fields resisting the
pull-in force on the associated armature when the solenoid is
energized. Certain designs have been proposed to address these
issues. Among them is the proposal to form slots in the flux ring
to create longer path lengths for eddy currents to travel. As a
result, the magnetic fields generated by the eddy currents may be
relatively weaker. While these strategies have seen some success,
there remains room for improvement.
SUMMARY OF THE INVENTION
In one aspect, a solenoid actuated device includes an actuator body
including a first body piece having a first clamping surface, a
second body piece having a second clamping surface, and a clamping
mechanism which includes a release state and a clamping state. The
solenoid actuated device further include a single-pole solenoid
actuator assembly positioned at least partially within the actuator
body and including a stator, an armature movable relative to the
stator, and a movable member coupled with the armature. The
single-pole solenoid actuator assembly further includes a-one-piece
compound armature housing having a load carrying component clamped
between the first clamping surface and the second clamping surface,
and a flux carrying component supported by the load carrying
component and defining a sliding air gap with the armature. The
load carrying component includes a high structural strength and a
low flux permeability, and the flux carrying component includes a
low structural strength and a high flux permeability.
In another aspect, a method of making a solenoid actuated device
includes establishing a magnetic flux path for a single-pole
solenoid actuator at least in part via placing an armature at an
axial air gap with a stator, and placing the armature at a sliding
radial air gap with a flux carrying component of a one-piece
compound armature housing. The method further includes establishing
a structural load path for the single-pole solenoid actuator at
least in part via placing a load carrying component of the
one-piece compound armature housing between a first actuator body
piece and a second actuator body piece. The method further includes
clamping the one-piece compound armature housing between the first
actuator body piece and the second actuator body piece.
In still another aspect, a method of operating a single-pole
solenoid actuated device includes supporting a stator, an armature
and a one-piece compound armature housing of a single-pole solenoid
actuated device, within an actuator body. The method further
includes supporting a flux carrying component of the one-piece
compound armature housing with a load carrying component of the
one-piece compound armature housing. The method further includes
channeling magnetic flux across a sliding air gap between the flux
carrying component and the armature, and channeling a clamping load
between a first actuator body piece and a second actuator body
piece through the load carrying component of the one-piece compound
armature housing.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a sectioned side diagrammatic view of a solenoid actuated
device, according to one embodiment;
FIG. 2 is a sectioned side diagrammatic view of a portion of the
device of FIG. 1;
FIG. 3 is a disassembled view of a compound armature housing,
according to one embodiment; and
FIG. 4 is a graph illustrating armature position over time for two
different single-pole solenoid actuator assemblies.
DETAILED DESCRIPTION
Referring to FIG. 1, there is shown a solenoid actuated device 10
according to one embodiment. Device 10 may include a hydraulically
actuated electronically controlled fuel injector, but many other
solenoid actuated devices are contemplated to fall within the scope
of the present disclosure. Device 10, hereinafter referred to as
fuel injector 10, may include an actuator body 12 having a
plurality of body pieces, including a first body piece 14 and a
second body piece 18. A single-pole solenoid actuator assembly 24
may be positioned at least partially within actuator body 12 and
includes a stator 26, an armature 28 movable relative to stator 26,
and a movable member 29 coupled with armature 28. In one
embodiment, movable member 29 may include a movable pin which
includes a valve control pin movable between a first pin position
and a second pin position. Fuel injector 10 may further include a
control valve mechanism 54 positioned at least partially within
second body piece 18 and being controllably coupled with movable
member 29. Second body piece 18 may further define a fuel inlet 56
of a type suitable for fluidly connecting fuel injector 10 with a
common rail of an internal combustion engine system, or with a unit
pump or the like as known in the art.
Actuator body 12 may further include a third body piece 58 wherein
an outlet check 88 of fuel injector 10 is positioned. Outlet check
88 may include a conventional needle check configured to move
between a closed position and an open position to fluidly connect
one or more nozzle outlets 59 with fuel inlet 56 in a known manner.
Control valve mechanism 54 may include a check control valve member
86 such as a ball valve. Valve member 86 may be movable in response
to moving movable member 29 via actuating single-pole solenoid
actuator assembly 24, again in a known manner.
In one embodiment, first body piece 14 may include a stator
housing, and second body piece 18 may include a valve body. Third
body piece 58 may include a nozzle body having one or more nozzle
body components which define nozzle outlet 59. As further described
herein, selection of materials for certain of the components of
fuel injector 10, as well as forming certain components with
particular geometries, is contemplated to provide a fuel injector
or other solenoid actuated device having robust magnetic and
structural properties.
To this end, actuator assembly 24 may further include a one-piece
compound armature housing 30 having a load carrying component 32
and a flux carrying component 34 supported by load carrying
component 32 within actuator body 12. Flux carrying component 34
may define a sliding air gap 36 with armature 28. Load carrying
component 32 and flux carrying component 34 may have different
structural, magnetic and electrical properties. In one embodiment,
load carrying component 32 may include a high structural strength
and a low flux permeability, whereas flux carrying component 34 may
have a low structural strength and a high flux permeability. Load
carrying component 32 may also include a relatively low electrical
resistivity, whereas flux carrying component 34 may have a
relatively high electrical resistivity, the significance of which
will be apparent from the following description. It should be
appreciated that the various properties of the respective
components such as flux permeability may vary based on part
geometry and/or operating characteristics of the associated system.
For instance, variance in factors such as electrical current or
voltage used in energizing solenoid actuator assembly 24, or
changes in part location, dimensions or shape, may result in
changes in the observed flux permeability of flux carrying
component 34 or load carrying component 32. Load carrying component
32 may be formed, for example, from a relatively hard, relatively
non-magnetic material such as stainless steel. Flux carrying
component 34 may be formed from a relatively soft, relatively
highly magnetic material such as a powder material comprised of
iron particles coated with a non-conducting material. Suitable
materials for forming flux carrying component 34 are available, for
example, under the trade name Somaloy.RTM.. As used herein, it
should be understood that the terms "relatively non-magnetic" and
"relatively highly magnetic" refer to electrically induced
magnetism as opposed to permanent magnetism.
It has been discovered that certain materials, such as those used
for flux carrying component 34 in a practical implementation
strategy, tend to be poorly suited for carrying loads, at least
when used in certain types of devices. Such materials tend to
crumble if subjected to repeated impacts with other components of
an associated system, and can structurally fail or deform if
subjected to loads. As will be further apparent from the following
description, the configuration of one-piece compound armature
housing 30 addresses these and other concerns.
Referring now also to FIG. 2, there is shown a portion of fuel
injector 10 enlarged and in greater detail as compared with FIG. 1.
As alluded to above, compound armature housing 30 may provide dual
services of channeling magnetic flux during operating actuator
assembly 24, and also channeling structural loads between and among
components of fuel injector 10. First body piece 14 may have a
first clamping surface 16, and second body piece 18 may have a
second clamping surface 20. Fuel injector 10 may further include a
clamping mechanism 22 having a release state and a clamping state,
and being configured to clamp compound armature housing 30 between
components of fuel injector 10. As mentioned above, first body
piece 14 may include a stator housing positioned about a stator 26
and a solenoid 90 of actuator assembly 24. First body piece 14 may
further include a first stator housing end 60 having first clamping
surface 16 located thereon, and a second stator housing end 62.
Load carrying component 32 may be clamped between first clamping
surface 16 and second clamping surface 20, in contact with first
clamping surface 16. In one embodiment, a spacer 48 may be
positioned axially between compound armature housing 30 and second
clamping surface 20, for reasons further described herein.
Actuator body 12 may further include a fuel injector cap 64 having
a third clamping surface 66 contacting second stator housing end 62
such that first body component/stator housing 14 is clamped between
fuel injector cap 64 and compound armature housing 30. In one
embodiment, clamping mechanism 22 may include a first set of
threads 68 which may be external threads located on fuel injector
cap 64, and a second set of threads which may be internal threads
70 located on second body piece 18. In other embodiments, clamping
mechanisms other than cooperating internal and external threads
might be used. Moreover, rather than locating threads 68 and 70 on
the body pieces shown in FIGS. 1 and 2, they might alternatively be
located on other body pieces of fuel injector 10 or at locations
other than those shown.
In one embodiment, compound armature housing 30 may be configured
to serve further functions beyond those of a flux carrier and a
structural load carrier. To this end, compound armature housing 30
may define a longitudinal axis A and include an outer radial
surface 38 and an inner radial surface 40 defining a guide bore 42
for movable member 29. Referring also to FIG. 3, compound armature
housing 30 may include a stepped configuration defining a first
axial segment 44 which includes flux carrying component 34 and load
carrying component 32, and a second axial segment 46 which includes
guide bore 42. A middle axial segment 47 may be positioned between
first axial segment 44 and second axial segment 46. When assembled
with actuator body 12 in fuel injector 10, first axial segment 44
may define a first radial air gap 50 between outer radial surface
38 and second body piece 18. Second axial segment 46 may define a
second radial air gap 52 between outer radial surface 38 and second
body piece 18. Second radial air gap 52 may be smaller than first
radial air gap 50 in one embodiment, for reasons further described
herein. Stator 26 may further include a first axial end surface 72
defining an axial air gap 74 with armature 28. Load carrying
component 32 may include a second axial end surface 76 contacting
each of first axial end surface 72 and first clamping surface 16. A
majority of second axial end surface 76 may contact first clamping
surface 16, with a relatively smaller part of second axial end
surface 76 contacting first axial end surface 72 of stator 26, in
one embodiment. In other embodiments, second axial end surface 76
may contact first clamping surface 16 but not contact first axial
end surface 72 at all.
Referring in particular to FIG. 3, flux carrying component 34 may
include a flux ring having an annular configuration and including a
flux ring inner radial surface 78. When mounted in load carrying
component 32 and positioned within actuator body 12 with other
components of fuel injector 10, inner radial surface 78 adjoins
sliding air gap 36. Flux carrying component 34 may further include
an outer radial surface 80 and a flux ring radial thickness t.sub.1
between inner radial surface 78 and outer radial surface 80. Flux
carrying component 34 may further include a chamfer 79 between
inner radial surface 78 and outer radial surface 80, and adjoining
inner radial surface 78, which assists in channeling magnetic flux
in a desired flux path into armature 28 rather than shorting to
stator 26. Load carrying component 32 may include a flux ring
support cup 33 configured to support flux carrying component 34,
and having a support cup inner radial surface 82 contacting flux
ring outer radial surface 80. Load carrying component 32 may
further include a support cup outer radial surface 84 and a support
cup radial thickness t.sub.2 between support cup inner radial
surface 82 and support cup outer radial surface 84 which is less
than flux ring radial thickness t.sub.1.
In one embodiment, a one-piece compound element having a flux
carrying component of Somaloy.RTM. or a similar material, and a
carrier component of steel, silicon iron, or the like, such as
compound armature housing 30, may be made by a process of insert
molding. As mentioned above, suitable materials for forming flux
carrying component 34 may include a powder of relatively highly
magnetic particles, each of which is encased in a non-conductive
material. Engineers have found it challenging to form such
materials into parts having sufficient structural integrity to
withstand the relatively harsh operating environments of a solenoid
actuator. As further described herein, insert molding such
materials in a carrier component has been discovered to provide a
practical implementation strategy for leveraging desirable magnetic
properties, while overcoming the sometimes undesirable structural
properties.
FIG. 3 depicts flux carrying component 34 and load carrying
component 32 as separate parts for illustrative purposes. In one
embodiment, flux carrying component 34 may be formed by pressing
suitable powder material to a near net shape, then positioning
component 34 in load carrying component 32, possibly retaining it
therein via Loctite.RTM. or another suitable adhesive. Where
compound armature housing 30 is formed by insert molding, however,
load carrying component 32 may serve as a mold, or part of a mold,
into which a powder material for flux carrying component 34 is
poured. In one embodiment Somaloy.RTM. powder may be poured into
flux ring support cup 33, and a suitably shaped pressing device
used to apply a compressive force to the Somaloy.RTM. powder. A
conventional powder metal press equipped with an appropriately
shaped tool to form component 34 to an approximate desired shape
may be used for this purpose. The compressive force will assist in
molding together the particles of the powder such that the
particles assume an annular shape approximately corresponding to
that of flux carrying component 34. The pressing force used may
depend at least in part on the end shape desired for the flux
carrying component, the thickness of the flux carrying component in
the direction of pressing force, and the intended service
application. In one embodiment, the powdered material of which the
flux carrying component is formed may be reduced in volume from a
starting volume of the powder to an end volume of the flux carrying
component by as much as 50%, although the present disclosure is not
thereby limited.
In certain instances, following pressing, exposed surfaces of the
flux carrying component might be ground or otherwise machined to
render the compound part having desired dimensions, surface shape,
and surface finish. In other instances, machining may not be
required. Other solenoid actuator components for which the use of
magnetic particles coated with non-conductive material is
considered advantageous, such as stators and armatures, may be made
by a similar insert molding process.
Once compound armature housing 30 is made, it may then be assembled
with other components of fuel injector 10. In particular, compound
armature housing 30 may be placed within second body component 18
with spacer 48 located between first axial segment 32 and second
clamping surface 20, as shown in FIG. 2. An assembly comprised of
armature 28 and movable member 29 may then be inserted into
compound armature housing 30 such that movable member 29 is
received in guide bore 42. Positioning armature 28 and movable
member 29 within compound armature housing 30 may include
positioning armature 28 at sliding radial air gap 36.
Other components of actuator assembly 24 may then be positioned
within second body component 18. In particular, stator 26 may be
positioned in first body component/stator housing 14, then the
assembly of first body component 14 and stator 26 and possibly
other components may be placed in second body component 18.
Positioning the assembly of first body component 14 and stator 26
within second body component 18 may include placing stator at axial
air gap 72 with armature 28, and may also be understood as
establishing a magnetic flux path P.sub.1. Positioning the subject
assembly may also be understood as establishing a structural load
path P.sub.2 for actuator assembly 24. With the components
positioned as described, first clamping surface 16 may contact load
carrying component 32, and spacer 48 may be positioned in contact
with each of first axial segment 42 and second clamping surface 20.
A stop 31 may be positioned to limit travel of movable member 29.
Fuel injector cap 64 may then be coupled with second body component
18 by engaging cooperating threads 68 and 70, until third clamping
surface 66 contacts axial end 62 of first body component 14, and a
clamping load applied.
In certain embodiments it may be desirable to magnetically isolate
compound armature housing 30 from second actuator body piece 18.
Placing compound armature housing 30 at radial air gap 50 and at
radial air gap 52 will position compound armature housing 30 such
that it does not contact second body piece 18 at all, at least in
certain embodiments. Accordingly, radial air gap 50 may prevent
magnetic flux from being channeled through load carrying component
32 and into second body piece 18. This avoids losing flux to
actuator body 12 which would otherwise be available to impart a
pull-in force on armature 28 when solenoid 90 is energized. It will
be recalled that first radial air gap 50 may be larger, for
example, radially thicker, than second radial air gap 52. This
design feature limits the likelihood of contact occurring between
second body piece 18 and first axial segment 34, since contact
would be more likely to occur, if at all, between second axial
segment 46 and second body piece 18. In other words, the relatively
tighter clearance between second axial segment 46 and second body
piece 18 than between first axial segment 44 and second body piece
18 will tend to inhibit inadvertent positioning of first axial
segment 44 in contact with second body piece 18, and thus inhibit
the channeling of magnetic flux through first axial segment 44 and
into second body piece 18.
INDUSTRIAL APPLICABILITY
Referring to the drawings generally, operating a single-pole
solenoid actuated device such as fuel injector 10 may include
supporting stator 26, armature 28 and compound armature housing 30
within actuator body 12. Load carrying component 32 may support
flux carrying component 34 within actuator body 12 when compound
armature housing 30 is positioned for service therein. Stator 26
may further include a solenoid 90 electrically connected with a set
of electrical terminals 67. When electrical current is applied to
electrical terminals 67 to energize solenoid 90, solenoid 90 may
generate a magnetic flux. Operating fuel injector 10 may thus
further include channeling magnetic flux in actuator assembly 24
according to magnetic flux path P.sub.1. Flux path P.sub.1 may pass
about solenoid 90, through stator 26, through flux carrying
component 34, across sliding air gap 36, and into armature 28. From
armature 28, the magnetic flux may be channeled across axial air
gap 74 and back into stator 26. As will be understood by those
skilled in the art, energizing solenoid 90 may cause armature 28 to
move towards stator 26 across axial air gap 74. Movable member 29
may contact stop 31 to limit travel of armature 28 towards stator
26 and prevent contact therewith. When solenoid 90 is de-energized,
armature 28 may move in a reverse direction away from stator 26,
under the influence of a return spring 19 coupled with movable
member 29.
Moving armature 28 by energizing solenoid 90 may further cause
movable member 29 to move from a first pin position to a second pin
position. This in turn may result in movement of valve member 86
from a first valve position to a second valve position by way of a
fluid pressure of fuel supplied via fuel inlet 56. Moving valve
member 86 may occur during moving movable member 29, and can result
in relieving a closing hydraulic pressure on outlet check 88 to
enable moving outlet check 88 from a closed position to an open
position to initiate fuel injection. De-energizing solenoid 90 will
tend to result in closing of outlet check 88.
Operating device 10 may further include channeling a clamping load
between first body piece 14 and second body piece 18 through load
carrying component 32 of compound armature housing 30. As discussed
above, clamping mechanism 22 may include cooperating threads 68 and
70 which enable fuel injector cap 64 to be urged downward against
first body piece 14, and thereby clamp compound armature housing 30
and spacer 48 between first clamping surface 16 and second clamping
surface 20. In FIG. 2, load path P.sub.2 is shown which includes a
first load path segment through first body piece 14, a second load
path segment through load carrying component 32, a third load path
segment through spacer 48 and a fourth load path segment through
second body piece 18.
Turning now to FIG. 4, there is shown a graph wherein the Y-axis
represents position and the X-axis represents time. The graph of
FIG. 4 includes a solid line Z illustrating example operation of a
conventional single-pole solenoid actuator assembly or device using
a solid piece of relatively uniform material as a flux carrying
component or flux ring, and a dashed line W illustrating example
operation of a single-pole solenoid actuator assembly or device
according to the present disclosure.
In FIG. 4, a time t.sub.1 represents initial solenoid energization
for each example device. A time t.sub.2 represents an end of
armature motion time at which an armature such as armature 28 in a
solenoid actuator assembly according to the present disclosure
reaches its position of maximum displacement, where movable member
29 contacts stop 31, for example. A time t.sub.3 represents an end
of motion time for the conventional device. It may be noted that a
relatively faster response time is associated with energizing a
solenoid actuator according to the present disclosure. Another time
t.sub.4 represents a start of armature motion time when a solenoid
for each example device is de-energized and the associated armature
begins to return toward its rest position. It may be noted that a
relatively faster response time is associated with de-energizing a
solenoid actuator according to the present disclosure. The device
according to the present disclosure ceases motion following
solenoid de-energization at a time t.sub.5, whereas the
conventional device ceases motion at a later time t.sub.6.
The improved, faster response of a device according to the present
disclosure is believed due at least in part to reduced eddy
currents. Since the electrical conductivity of flux carrying
component 34 is less than that of conventional flux ring materials
the generation of eddy currents which produce problematic magnetic
fields is reduced. As a result, when magnetic flux is generated by
energizing solenoid 90, or when flux decays by de-energizing
solenoid 90, armature 28 is less affected, if at all, by eddy
current-generated magnetic fields or residual magnetism, in
comparison with earlier designs having uniform, solid flux rings
and even slotted flux rings. In the particular case of actuators
used for certain applications such as valve control in a fuel
injector, relatively more precise and predictable operation will be
possible than in earlier systems.
The present description is for illustrative purposes only, and
should not be construed to narrow the breadth of the present
disclosure in any way. Thus, those skilled in the art will
appreciate that various modifications might be made to the
presently disclosed embodiments without departing from the full and
fair scope and spirit of the present disclosure. Other aspects,
features and advantages will be apparent upon an examination of the
attached drawings and appended claims.
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